Brake



Jun 4, 1929. w B N I 1,716,026

BRAKE Filed Aug 26, 1926' v glwumtoz Patented June 4, 1929. g I

UNITED STA res PATENT oFFIcE.

wILLIAMr. BONNER, or 'rnnnroiv, NEW JERSEY, assrenon To A. r. COLGREN, or

" CHICAGO,

ILLINOIS.

BRAKE.

Application filed August 26,1926. Serial No. 131,748.

This invention relates, to brakes; and it comprises a brake having an iron' or steel annulusor drum as the braked member and an engaging braking member located either ifi side or outside the drum, the engaged face of the drum carrying a strip of mineral matter of low heat conductivity, usually asbestos, said strip acting both as a friction member and as a heat insulating layer, and the nonengaged face being exposed for free heat radif ation,said exposed face being often provided with means for facilitating radiation; all as 'more fully hereinafter set forth and as claimedi- For the sake of strength, brakes are ordinarily made of iron or steel'which are metals of relatively low heatconductivity, and disposition ofithe great amount of' heat developed in braking is sometimes a serious problem. In an ordinary type of brake, strengthened asbestos is used as a friction lining. Asbestos is of minera nature and does 'not burn or' spark. Sometimes it is reinforced with wire; sometimes a binder, such as rubber, having good tensile strength is eniployed. Asbestos, being a material of low heat conductivity, the heat developed on the face of the lining strip, although it does pass into its body, does not pass rapidly. Its heat conductivity however increases as the temperature'rises. 1

A common type of brake uses .a drum as the braked member, braking being effected by an outside flexible strap and an inside expansible member, each carrying anv asbestos friction facing. The difiicultywith this structure is that the drum being, so to speak, double heated, in any heavy duty braking may become dangerously hot; and especially at the surface. A better arrangement is that disclosed and claimed in my prior Patent No. 1,426,543, August 22, 1922, where the asbestos facing is transferred from the braking members to the drum. Here it acts as a sort of heat insulation for the heavy metal of the drum.

The braking members are commonly of comparativelylightmetal construction and d1s sipate heat more readily than does the drum.

In certain relations, however, and especially in heavy duty work, as in truck brakes, oil well brakes, and the like, where the amount of energy to be dissipated is great or braking is continued over a relativelv long time, it

is found in practice that the drum heats up. .As stated, heat goes through the asbestos to some extent and in this structure it accumw.

lates in the drum element faster than it can .be dissipated therefrom, so that the drum temperature builds up.

In-the present inventionf-I' have provided an'improvement on the brake of my prior patent, In the said patent both facesof the drum, the inner and the outer, are covered by the asbestos composition. I find that for some work, it is better to abandon using both faces .for braking and leave one face clear or naked for heat radiation. By so' doing, the retained asbestos facing on one side acts to prevent communication of much of the friction heat to the drum, while the free face of the drum, radiates the heat that does penetrate through the asbestos layer. In other words, the asbestos facing acts to prevent most of the heat gaining access to the metal of the drum, while such heat as does penetrate the asbestos and reach the drum is given an opportunity to escape. Heat radiation may be facilitated by finning, corrugating, or otherwise specially shaping the exposed radiating face. It is best to have it of black iron and not polished. Rough surfaces dissipate heat more rapidly than smooth. The same considerations apply to the braking member. Blackheat-ra'diatmg paints or coatings, such as graphite, are sometimes useful. Sand blasting togive a roughened'surface is also often useful.. p The asbestos friction member may be of any of'the usual types employed in the brak-. ing art; such as asbestos spun over wire and woven into fabric; laminated fabric containing wire fabric, plastic compositions made with asbestos and such binders as rubber,

linseed oil, etc. Using asbestos in the present invention as a layer on the braked element, not so much tensile strength is required as where it occurs as a. layer on the braking member. Thestrai'ns are mostlycompression strains andgno flexibility is necessary.-

tain embodiments of the is used as an interior facing, the usual types of expansible braking members may be employed; where it is an outer facing, the usual strap types of braking elements may be used. In the accompanying illustration have shown, more or less diagrammatically, cer- In this showing, U

Figure 1 is a transverse sectional view through a brake embodying my invention-and employing an external contracting brake v F igure2 is a partial sectional view taken along the line 2-2 of Figure 1 Figure 3 is a similar view of ZL'IIlOdlfiBd form of my invention adapted for use with an internal expanding brake shoe;

Figure 4 is a fragmentary view, partly 1n section, ofa brake comprising the present 1nvention applied to the cable drum of ahoist,

the interior face of the brake flange being the area of its surface; and

Figure 5 is afragnmentary detail view of a brake drum, the interior face of which is transversely corrugated to increase its surface area. Referring to the draw ngs:

In Fig. 1, friction faclnntl, of strengthened asbestos or similar heat 'r'esisting material or compound of low heat conductivity, is permanently attached to the outer face of, a flange 2 which is an integral part of a'brake drum 3, the opposite inner face 4 of the flange being naked and exposed for the purpose of dissipatin heat which is generated by application of t e brake. The exposed face of the flange may be bare and, it is advantageously of black iron or steel for the purposepf assisting radiation and rapid dissipation of heat, and I have sometimes found it advantageous to roughen this face or coat it with graphite or a dark colored paint. Both ex pcdients may be Used. A dark rough surface radiates heat more rapidly than one which is polished or of 'a light color. Sun rounding the brake drum, and spaced from the friction facing which is mounted on it, is a brake band 5 which, when it is contracted, frictionally engages the facing of the drum and effectively stops rotation.

A modified form of invention is shown in Fig. 3 wherein a friction facing 6 is atfixed to the inner face of a brake drum 7, the outer face of which is formed with a plurality of' heat radiating fins 8 for the purpose of cooling the exposed face of the brake drum. An expanding brake member 9 is provided inside the flange of the drum to coact with the friction facingcarried thereby.

While these showings are of automobile brakes, it is to be understood that the use of my inventionis not confined to brakes for this purpose. The invention has been found to be particularly adaptable to hoists employing a present invention.

period cable drum, especially those hoists which are used in oil well drilling operations, wherein a cable with drilling-tools must be slowly lowered through long distances, and continuous braking effected for long periods of time.

In hoist brakes, the friction lining often wears or burns out rapidly for the reason that the brakes are constantly applied and the heat generated cannot be quickly dissipated. Heat development may be continuous over a long of time andthe metal of a double faced brake may become dangerously hot. It

must be remembered that, as stated, as the I temperature of the asbestos rises, its conductivity for heat increases. The temperatures of. the friction face of the asbestos may rise to a .point where it becomes a conductor of heat rather than an insulator and quickly transmits the heat generated to the metal of, the drum. By providing a naked face on the drum, or one which is roughened or undulatory for dissipationof heat, the drum acts to keep the base of the asbestos face cool and prevents this rise ofheat conductivity. "In such brakes in the present invention there may be, as shown in Fig. 4, a cable drum 10 with aflange 11 which comprises the brake drum, and which is faced with a friction ma terial 12 (if the, kind above described. The under or exposed face 13 of the flange is formed with annular corrugations as shown, or it may be, formed with transverse corrugations 14 as shown in Fig. 5, and thereby capable of quickly dissipating heat generated by protracted application of the brake shoe because of its increased radiating surface. A metal band 14 surrounds the friction facing of the brake drum, and is contracted to engage it andthereby stop rotation when the brake is applied. i

The advantage to be gained by coating. roughening, or increasing the surface area of that face of a brake drum which radiates the heat generated varies according to thecharacter of the brake and the mount of work which itmust perform in stopping rotation. For heavy duty it'is preferable, though not necessary, that the heat radiating surface of the brake drum be roughened or corrugated to increase its surface area, or blackened to promote its heat radiating properties, whereas for light duty brakes even a plain polished surface may dissipate the heat sufficiently effectivel Asbestos is ordinarily employed in forming friction facingsunder the present invenfor heat radiation;

'ing

forcemen't may be used liberally provided the use'is not in such a way as to make the friction facing unduly conductive for heat.

radiation.

2. In combination with braking and braked elements, a mineral facing of low heat conductivity aflixed to one face of said braked element which is presented to the braking element, the other face being naked.

3. In a combination with braking and braked elements, a flange on said braked element, a mineral facing of low heat conduc-- tivity aflixed to one surface of said flange for coaction with saidbraking element, the opposite surface of said 4. In combination with aibrake drum hav an annular flange, a minera'l facing of low heat conductivity aflixed to the outer face of said flange, a contacting-braking element coactmg with said'mineral facing, the inner flange being adapted face Ofs'aid flange being adapted for heat radiation.

.5. A brake comprising coacting, braking, and braked elements, means for causing braking engagement of said elements, a heat resisting mineralnlaterial'of low heat conductivity aflixed to one face of-the braked element and heat dissipating means associated with the other face of said element.

6. A brake comprising coacting, braking, v

and braked elements, means for causing braking engagement of said elements, a heat.

resisting mineral material of-low heat o0nductivity aflixed to one face of the braked element. and fins on the other face of said-element.

- 7. A brake comprising coacting', braking,

and braked lements, means for causing braking engagement of said elements, a heat resisting mineral material of low heat conductivity aflixed to one face' of the braked element and rough heat radiating surface;

I 8. A brake drum provided'with attached asbestos resistance material on onesurface only.

fixed my signature. WILLIAM T. BONNER.

the other face provided with a testimony. whereof, I have hereunto a ff 

